Aloe is the dried juice collected by incision, from the bases of the leaves of various species of Aloe. Aloe perryi Baker, Aloe vera Linn or Aloe barbadensis Mil and Aloe ferox Miller., belonging to family Liliaceae.
ALOE
Biological Source
Aloe is the dried juice collected by incision, from the
bases of the leaves of various species of Aloe. Aloe perryi Baker, Aloe vera Linn
or Aloe barbadensis Mil and Aloe ferox Miller., belonging to family Liliaceae.
Aloe perryi Baker is found in Socotra and
Zanzibar islands and in their
neighbouring areas and so the aloes obtained from this species is known as
Socotrine or Zanzibar aloe. Aloe vera Linn
is also known as Aloe vulgairis Lamarek,
or Aloe barbadensis Mil. or Aloe officinalis Forskal. It was
formerly produced on the island of
Barbados, where it was largely cultivated, having been introduced at the
beginning of the sixteenth century. It is now almost entirely made on the Dutch
islands of Curacoa, Aruba and Bonaire. The aloes obtained from this species is
known as Curacao or Barbados aloe. Aloe
ferox Miller and hybrids of this species with Aloe africana and Aloe spicata, A. platylepia and other
species of Aloe grows in Cape Colony
and so is known as Cape aloe.
Geographical Source
Aloes are indigenous to East and South Africa, but have been
introduced into the West Indies and into tropical countries, and will even
flourish in the countries bordering on the Mediterranean.
Cultivation and Collection
It is an evergreen perennial growing to 0.8 m by 1 m at a
slow rate. The plant prefers light (sandy) and medium (loamy) soils, requires
well-drained soil and can grow in nutritionally poor soil. The plant prefers
acid, neutral and basic (alkaline) soils. It cannot grow in the shade. It
requires dry or moist soil and can tolerate drought. They are xerophytic plant.
It can be propagated by seeds. Seeds are sown in the spring in a warm green
house. The seed usually germinates in 1–6 months at 16°C. The seedlings are
transferred to the pots containing well-drained soil. They are allowed to grow
in sunny part for at least their first two winters. The offsets will be
available, usually in spring. The plants produce offsets quite freely and they
can be divided at any time of the year as long as it is warm enough to
encourage fresh root growth to allow reestablishment of the plants. Young
offsets are planted in the soil after the rainy season in rows situated at a
distance of 60 cm.
In the second year leaves are collected by the natives by
protecting their hands because of the spiny nature of leaves. The leaves are
cut near the base, kept inside of kerosene tins and taken them to a central
place for the preparation of aloe. Juice of aloe is present in parenchymatous
cells of pericycle that are mucilage cells. In a single incision mucilage cells
exert pressure on pericycle cells and the entire juice from the leaves is
drained out.
Preparation of Aloe
Curacao
or barbados aloe
In West Indies the cut leaves are arranged with their cut
surface on the inner side, on the sides of V shaped vessel of about 1–2 m long
and the flowing juice is collected in a tin vessel that is placed below the
V-shaped vessel This juice thus collected is concentrated either by spontaneous
evaporation, or more generally by boiling until it becomes of the consistency
of thick honey. These conditions favours the crystallization of barbaloin and
this aloe contains crystals of barbaloin because of the presence of which it
becomes opaque and so also known as hepatic or livery aloe. On cooling, it is
then poured into gourds, boxes, or other convenient receptacles and solidifies.
Socotrine
aloe
When it is prepared, it is commonly poured into goat skins,
and spontaneous evaporation is allowed for about a month when it becomes
viscous pasty mass which are then packed into cases. In European countries it
is dried in wooden pans with hot air till moisture is about 10%.
Zanzibar
aloe
This aloe is prepared similar to Socotrine aloe. It is
packed in skins, of carnivorous animals. This aloe is also known as monkey skin
aloe.
Cape
aloe
The leaves of the plants from which Cape aloe is obtained
are cut off near the stem and arranged around a hole in the ground, in which a
sheep skin is spread, with smooth side upwards. When a sufficient quantity of
juice has drained from the leaves it is concentrated by heat in iron cauldrons
and subsequently poured into boxes or skins in which it solidifies on cooling.
Large quantities of the drug are .exported from Cape Town and Mossel Bay.
Characteristics
Curacao
aloe
It is usually opaque and varies in colour from bright
yellow-ish or rich reddish brown to black. Sometimes it is vitreous and small
fragments are then of a deep garnet-red colour and transparent. It is then
known as ‘Capey Barbados’ and is less valuable, but may become opaque and more
valuable by keeping. Curacoa Aloes possesses the nauseous and bitter taste that
is characteristic of all Aloes and a disagreeable, penetrating odour. It is
almost entirely soluble in 60% alcohol and contains not more than 30% of
substances insoluble in water and 12% of moisture. It should not yield more
than 3% of ash. The fracture is waxy.
Socotrine
aloes
It may be distinguished principally from Curacoa Aloes by
its different odour. Much of the dry drug is characterized by the presence of
small cavities in the fractured surface; it is yellow-brown to dark-brown in
colour and opaque. Fracture is irregular and porous and taste is bitter.
Zanziber
aloes
Zanzibar Aloes often very closely resembles Curacoa in
appearance and is usually imported in liver-brown masses which break with a
dull, waxy fracture, differing from that of Socotrine Aloes in being nearly
smooth and even. It has a pleasant odour and bitter taste.
Cape
aloes
It forms dark coloured masses which break with a clean
glassy fracture and exhibit in their splinters a yellowish, reddish-brown or
greenish tinge. Its translucent and glossy appearance are very characteristic
and red-currant like odour sufficiently distinguish it from all other varieties
of Aloes.
Chemical Constituents
The most important constituents of Aloes are the three
isomers of Aloins, Barbaloin, β-barboloin and Isobarbaloin, which
constitute the so-called ‘crystalline’ Aloin, present in the drug at from 10 to
30%. Other constituents are amor-phous Aloin, resin, emodin and Aloe-emodin.
Barbaloin is present in all the varieties; it is slightly yellow coloured,
bitter, water soluble, crystalline glycoside. Isobarbaloin is a crystalline
substance, present in Curacao aloe and in trace amount in Cape aloe and absent
in Socotrine and Zanzibar aloe. The chief constituents of Socotrine and
Zanzibar aloe are Barbaloin and β-Barbaloin.
Chemical Tests
Boil 1 gm of drug with 100 ml water, allow it to cool; add 1
gm kieselguhr, stir it well and filter through filter paper.
1. Borax
Test: Take 10 ml
of aloe solution and to it add 0.5 gm
of borax and heat; a green coloured fluorescence is produced indicating the
presence of aloe-emodin anthranol.
2. Modified
Anthraquinone Test: To
0.1 gm of drug, 5 ml of 5% solution
of ferric chloride is added followed by the addition of 5 ml dilute hydrochloric
acid. The mixture is heated on water bath for 5–6 min and cooled. An organic
solvent (benzene or chloroform) is added and shaken. Separate the organic
solvent layer and add an equal volume of dilute ammonia. The ammoniacal layer
produces pinkish red colour.
3. Bromine
Test: To 5 ml of
aloe solution, add equal volume of
bromine solution; bulky yellow precipitate is formed due to the presence of
tetrabromaloin.
4. Nitrous
Acid Test: To
5 ml of aloe solution, add little of
sodium nitrite and few drops of dilute acetic acid; it produces Pink or
purplish colour. Zanzibar and Socotrine aloes give negative test.
5. Nitric
Acid Test: 2
ml of concentrated nitric acid is added
to 5 ml of aloe solution; Curacao aloe gives deep reddish-brown colour,
Socotrine aloe gives pale yellowish-brown colour, Zanzibar aloe gives
yellowish-brown colour and Cape aloe first produces brown colour which on
standing changes to green.
6. Cupraloin
Test: 1 ml of the
aloe solution is diluted to 5 ml with
water and to it 1 drop of copper sulphate solution is added. Bright yellow
colour is produced which on addition of 10 drops of saturated solution of
sodium chloride changes to purple and the colour persist if 15–20 drops of 90%
alcohol is added. This test is positive for Curocao aloe, faint for Cape aloe
and negative for Zanzibar and Socotrine aloes.
Uses
The drug Aloes is one of the safest and stimulating
purga-tives, in higher doses may act as abortifacient. Its action is exerted
mainly on the large intestine; also it is useful as a vermifuge. The plant is
emmenagogue, emollient, stimu-lant, stomachic, tonic and vulnerary. Extracts of
the plant have antibacterial activity. The clear gel of the leaf makes an
excellent treatment for wounds, burns and other skin disorders, placing a protective
coat over the affected area, speeding up the rate of healing and reducing the
risk of infection. To obtain this gel, the leaves can be cut in half along
their length and the inner pulp rubbed over the affected area of skin. This has
an immediate soothing effect on all sorts of burns and other skin problems.
Substituents and Adulterants
A. candelsbmm (Natal aloes) is dull greenish black
to dull brown in colour, opaque. When
scraped it gives a pale greyish green or a yellow powder. It can be distinguished
as it gives negative test to borax test and produces a deep blue colour.
Jafferabad aloes and the Mocha aloes are the other two type of aloe which is
used as adulterant.
Marketed Products
It is one of the ingredients of the preparations known as Diabecon,
Evecare (Himalaya Drug Company), Mensonorm (Chirayu Pharma) and Kumari Asava
(Baidyanath).
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